With high integration of semiconductor devices and miniaturization of patterns, it has been required to further lower resistance of gate electrodes. There is known, as a method for further lowering the resistance of gate electrodes, a method in which a gate electrode is silicided by a self-aligned silicide (SALICIDE) technique.
In the silicon semiconductor industry, there is often employed a method in which a surface of a silicon layer is modified with a silicide of other kinds of metals such as Co, Ni, Au, Ag, Ti, Pd and Al so as to form an ohmic contact by a work function of an interface between a wiring metallic material and silicon. It is known that a crystalline cobalt silicide is suitable as this silicide from the viewpoint of specific resistance of the silicide per se and matching of a lattice constant with silicon (JP 8-116054 A).
A process for forming a cobalt silicide is commonly carried out by a method in which a vacuum process is used in any step in the process. There are known, as a method for forming a cobalt silicide using a vacuum process, for example, a solid-phase growth method (S. Saitoh et al., Appl. Phys. Lett. 37, 203 (1980)), a molecular beam epitaxy method (J. C. Bean et al., Appl. Phys. Lett. 37, 643 (1980)), an ion implantation method (A. E. White et al., Appl. Phys. Lett. 50, 95 (1987)) and the like. However, all of these methods require a large-scale device for deposition of at least one of silicon and cobalt in a gas phase, and they have a problem of high production costs. Since particles and oxides are likely to be formed, it is difficult to form a coated film on a large-area substrate. Moreover, it is essential to use, as a raw material, a compound which is converted into a gas under vacuum. Therefore, the kind of a raw compound is restricted and a highly sealable vacuum device is required, resulting in higher production costs.
There has recently been reported a technique in which a liquid composition is applied on a substrate to form a coated film, and then the coated film is heated to form a cobalt-silicon alloy film (JP 2003-313299A). This technology is an excellent technology which can form a cobalt-silicon alloy film by a simple method without using a vacuum process. However, the cobalt-silicon alloy film formed by this technology is mainly intended to be used as a wiring material having arbitrary resistance, and crystallization of the film is not taken into consideration.
A method for forming a crystalline cobalt silicide in a simple manner, which can be employed as an electrode material in a semiconductor device and the like, is still unknown.